The invention relates to swirl chambers for separating gas mixtures of the type having a feed port issuing tangentially into the chamber for the gas mixture, an extraction element extending from the area of the inner wall of the chamber for the heavy gas fraction, and a second extraction element extending from the inner central area of the chamber for the light gas fraction.
Among the feasible processes proposed for separating gas mixtures and isotope mixtures has been the swirl tube process. In certain contemplated arrangements a gas jet is introduced tangentially into a fixedly arranged tube. Rotation of the gases aided by the potential whirl effect causes the heavy particles to be separated from the light particles as a result of the centrifugal pressure field.
For implementing this process, a swirl chamber has been proposed which takes a conical shape and has an end wall at the major-diameter end. At this end, inclined inlet ports are provided at a tangent to the end wall through which the gas mixture is introduced. Owing to the circular cross-section of the chamber the medium is caused to rotate and flow azimuthally in the direction of the chamber axis towards the opposite end. At this minor-diameter end the heavy gas fraction is extracted while the light gas fraction rotating in the inward areas flows back axially and is exhausted through an extraction pipe extending through the front wall of the whirl or swirl chamber. This process provides a disadvantage, however, in that the angular momentum is diminished by wall friction and that, moreover, turbulent flow and attendant remixing losses are produced, making the separation work very poor despite the higher gas inlet velocity.
A broad aspect of the present invention is to provide an improved swirl chamber of the type noted above which achieves high separating outputs. It is a particular object of especially preferred embodiments of the present invention to achieve this aspect by means of a swirl chamber having a rotationally symmetrical, rotatably supported container. In preferred embodiments the wall of the chamber is caused to rotate in the rotational direction of the gas, so that when the two speeds are equaled, the wall friction is reduced to zero. This permits a largely laminar, helical flow of high velocity to be achieved, enabling effective separation of the heavy from the light gas particles.
To facilitate manufacture, certain preferred embodiments utilize a swirl chamber in the shape of a tubular cylinder. Because of the negligible wall friction the gas stream will maintain the angular momentum it had upon entering throughout its course in the swirl chamber. In certain other preferred arrangements, however, the swirl chamber or container is given a conical shape, so that the reduction in diameter will accelerate the gas stream and so increase the angular momentum for additionally improved separating work.
In a preferred embodiment of the present invention the container is driven by a gas jet, for which use is made particularly of process gas which is to be separated. In this arrangement, the container is surrounded by a stationary wall provided with tangentially directed nozzles allowing the motive gas to flow through the wall and impinge on slots or vanes of the container. These passageways may concurrently form the inlet ports for the feed gas. This will obviate the need for separate manufacturing provisions for the gas ducts on the one hand and cause the circumferential speed of the container to attain the inlet velocity of the process gas on the other.
In a further aspect of the present invention the container is preferably supported by gas and preferably imbedded in a gas cushion surrounding the container shell. The absence of friction with this arrangement prevents the inlet energy of the process gas from being diminished, so that the co-rotating swirl chamber achieves a notable gain in efficiency over previously disclosed stationary swirl chambers.
In certain preferred embodiments, for supporting the container, use is made of the process gas as it is for driving it, the process gas being diverted either from the fresh gas or from the swirl chamber. The bearing may optionally be pressurized also by these two measures combined.
To improve the starting and emergency performance, a sliding layer, preferably of graphite, is provided on the inner side of the stationary wall surrounding the container.
A further improvement in efficiency is achieved by making the swirl chamber a double chamber having a common gas inlet arranged in the central area according to certain preferred embodiments. This obviates the need for one front wall, so that the potential swirl required for separation of the components may develop more fully. The double chamber is preferably made to taper at the two ends. This will augment the angular momentum of the whirl flow and additionally cause the supporting gas surrounding the container to impose a measure also of axial pressure on the container, ensuring smooth and stable rotation of the swirl chamber also in the absence of a separate axial bearing.
With the double swirl chamber the heavy gas fraction is extracted at the two ends, where suitable outlet ports are provided. The light fraction is extracted through pipes which are either inserted into the chamber from the front sides of the container or which are arranged centrally in the chamber to catch the flow of light gas fraction directed axially towards the center of the chamber on both sides. It is an additional advantage if the extraction pipes are made to co-rotate as integral parts of the container according to certain preferred embodiments. This serves to prevent friction losses also at the extraction system.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.